Vehicle Brake Device

Abstract

To suppress the false evaluation of the braking performance failure by a braking performance evaluation system which evaluates the braking performance based on the matching degree related to correlation between the braking operation amount and the generated braking force as much as possible.SOLUTION: A vehicle braking apparatus 11 includes: a master cylinder device 14; a motor cylinder device 16; normally-open type shut-off valves 60a, 60b which are provided so as to be intervened in piping tubes 22a, 22d connecting the master cylinder device 14 with the motor cylinder device 16 and operate to open or close a hydraulic path; a determination part 75 which determines whether the brake pad temperature Tpad when the required boost request is made exceeds a first load threshold Tpadth1; and a braking control unit 77 which performs drive control to shut off the shut-off valves 60a, 60b based on the required boost request. The braking control unit 77 performs non-silent control by using a first closing valve transient characteristic in a case where the brake pad temperature Tpad when the boost request is made exceeds the first load threshold Tpadth1.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a vehicle braking device that applies a braking force to a vehicle. [Background technology]

[0002] For example, electric vehicles use a by-wire brake system that generates braking force via an electrical system in addition to the existing brake system that applies braking force via a hydraulic system. In such a by-wire brake system, the driver's brake pedal operation amount is converted into an electrical signal and given to an electric actuator that drives a piston of a slave cylinder (hereinafter referred to as a "motor cylinder device").

[0003] Then, the actuation of the electric actuator drives the piston, generating brake fluid pressure in the motor cylinder device. The brake fluid pressure thus generated operates the wheel cylinders, thereby applying a braking force to the vehicle (see, for example, the vehicle brake device in Patent Document 1). According to the by-wire type vehicle brake device disclosed in Patent Document 1, braking force can be applied to the vehicle via an electrical system.

[0004] In the by-wire type vehicle brake device disclosed in Patent Document 1, a solenoid valve that drives a plunger connected to a valve toward a valve-closed position against the spring force of a return spring is provided in a hydraulic line that communicates between a master cylinder and a motor cylinder device. The solenoid valve blocks primary hydraulic pressure generated in the master cylinder in response to the driver's braking operation, and generates secondary hydraulic pressure in the motor cylinder device according to the amount of brake pedal operation. The solenoid valve used is of the normally open type in order to ensure a fail-safe function.

[0005] To close a normally open solenoid valve, power must be supplied to generate the thrust necessary to keep the plunger, which receives the reaction force of the return spring, in the closed position and close the valve. When power is supplied to the solenoid valve, a collision noise occurs between the plunger and the case when the plunger reaches the closed position. In addition, when the power supply is stopped and the plunger is returned to its initial position, a collision noise occurs between the plunger and the case due to the spring force of the return spring.

[0006] In order to reduce such collision noise, the by-wire vehicle brake device according to Patent Document 1 includes a control device that controls the opening and closing of a solenoid valve in response to braking operation. This control device performs control to gradually increase the current supplied to the solenoid when driving the plunger toward the valve-closed position. For convenience of explanation, this type of control is called silent control. This silent control suppresses the speed at which the plunger reaches the valve-closed position.

[0007] According to the by-wire type vehicle brake device of Patent Document 1, the speed at which the plunger reaches the valve closing position is suppressed by the noise reduction control, thereby reducing the impact sound (noise) generated by the operation of the solenoid valve. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2012-131438 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the by-wire vehicle brake device according to Patent Document 1, the speed at which the plunger reaches the valve-closed position is suppressed by the silent control, impairing the responsiveness of the solenoid valve, which results in a time delay in blocking the hydraulic path, impairing the consistency of the correlation between the braking operation amount and the generated braking force.

[0010] Here, when a braking performance evaluation system is adopted that evaluates braking performance based on the consistency of the correlation, there is a risk that the braking performance evaluation system may erroneously evaluate a decline in braking performance in a driving scene with a large braking load, such as when going down a long downhill road.

[0011] The present invention has been made in consideration of the above-mentioned situation, and has an object to provide a vehicle braking device that can minimize erroneous evaluation of poor braking performance by a braking performance evaluation system that evaluates braking performance based on the degree of consistency related to the correlation between the generated braking force and the amount of braking operation. [Means for solving the problem]

[0012] In order to achieve the above object, the invention pertaining to (1) is a vehicle braking device that applies a braking force to a host vehicle, the vehicle braking device comprising: a master cylinder device that generates a primary hydraulic pressure in accordance with a braking operation by a driver; a motor cylinder device that generates a secondary hydraulic pressure corresponding to a target braking force by the operation of an electric actuator in accordance with a required boost request; a normally open solenoid valve that is provided in a hydraulic passage that communicates between the master cylinder device and the motor cylinder device and operates to open or close the hydraulic passage; and a control unit that performs drive control to close the solenoid valve based on the required boost request, the vehicle braking device providing a braking force to a host vehicle, the vehicle braking device being configured to apply a braking force to a host vehicle when the braking load when a boost request is generated is steady. The control unit executes braking control using a first valve-closing transient characteristic that starts from the time when the boost request is generated and ends up closing the solenoid valve when the braking load at the time when the boost request is generated exceeds a predetermined first load threshold value, and the first valve-closing transient characteristic is set steeper than a second valve-closing transient characteristic that starts from the time when the boost request is generated and ends up closing the solenoid valve when the braking load at the time when the boost request is generated falls in the steady region. The determination unit further determines whether the braking load when a boost request is generated exceeds a predetermined second load threshold, the second load threshold being set to a value higher than the first load threshold, and if the braking load when a boost request is generated exceeds the second load threshold, the determination unit determines that the braking load falls within a warning range that exceeds the warning range. This is its most important feature. Effect of the Invention

[0013] According to the vehicle braking device of the present invention, even when a braking performance evaluation system is adopted that evaluates braking performance based on the degree of consistency related to the correlation between the generated braking force and the braking operation amount, erroneous evaluation of poor braking performance by the braking performance evaluation system can be suppressed as much as possible. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of a vehicle braking device according to an embodiment of the present invention; [Diagram 2] 1 is a block diagram showing a configuration including an ESB-ECU and an integrated ECU provided in a vehicle braking system according to an embodiment of the present invention, and their surroundings. [Diagram 3] FIG. 4 is a flow chart illustrating the operation of the vehicle braking device according to the embodiment of the present invention. [Figure 4] FIG. 4 is a time chart illustrating the operation of the vehicle braking device according to the embodiment of the present invention. [Diagram 5] 5A to 5C are explanatory diagrams illustrating the operation of a vehicle braking device according to a comparative example of the present invention and the operation of a vehicle braking device according to the embodiment of the present invention in comparison with each other; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle braking device according to an embodiment of the present invention will now be described in detail with reference to the drawings. In the drawings shown below, components having a common function or components having corresponding functions are generally given the same reference numerals. For the sake of convenience, the size and shape of the components may be exaggerated or distorted.

[0016] [Summary of the vehicle braking device 11 according to the embodiment of the present invention] First, the gist of a vehicle braking device 11 according to an embodiment of the present invention will be described. In the vehicle brake device 11 according to the embodiment of the present invention, when the braking load Tpad at the time when the boost request is generated is in the warning region exceeding the steady region, the brake control is performed using a first valve closing transient characteristic that closes the solenoid valves 60a, 60b from the time when the boost request is generated. The first valve closing transient characteristic is set steeper than the second valve closing transient characteristic that closes the solenoid valves 60a, 60b from the time when the boost request is generated when the braking load Tpad at the time when the boost request is generated is in the steady region. As a result, even when a braking performance evaluation system that evaluates braking performance based on the consistency related to the correlation between the braking operation amount and the generated braking force is adopted, it is possible to minimize erroneous evaluation of poor braking performance by the braking performance evaluation system (see Figure 5). Hereinafter, the vehicle braking device 11 according to the embodiment of the present invention will be described in detail one by one.

[0017] [Schematic configuration of a vehicle braking device 11 according to an embodiment of the present invention] Next, a schematic configuration of a vehicle braking device 11 according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of a vehicle braking device 11 according to an embodiment of the present invention. The vehicle braking device 11 includes a by-wire type brake system that generates braking force via an electrical system, in addition to an existing brake system that generates braking force via a hydraulic system.

[0018] As shown in FIG. 1, the vehicle braking device 11 is configured to include a master cylinder device 14, a motor cylinder device 16, a vehicle stability assist device 18 (hereinafter referred to as the "VSA device 18," where VSA is a registered trademark), and hydraulic braking mechanisms 24FR, 24RL, 24RR, and 24FL. When the hydraulic braking mechanisms 24FR, 24RL, 24RR, and 24FL are collectively referred to, they will be abbreviated as "hydraulic braking mechanisms 24."

[0019] The master cylinder device 14 has a function of generating a primary hydraulic pressure according to a braking operation by a driver of the vehicle (not shown) via the brake pedal 12. To realize this function, the master cylinder device 14 is configured to include a master cylinder 34 that converts the braking operation of the driver input via the brake pedal 12 into a primary hydraulic pressure, a stroke simulator 64 that creates a pseudo reaction force against the brake pedal 12 depressed by the driver, and first to third shutoff valves 60a, 60b, 62. The first and second shutoff valves 60a, 60b correspond to the "solenoid valves" of the present invention. The functions of the first and second shutoff valves 60a, 60b will be described in detail later.

[0020] The motor cylinder device 16 has a function of generating a secondary hydraulic pressure corresponding to a target braking force (target braking torque) by operation of the brake motor (electric actuator) 72. In order to realize such a function, the motor cylinder device 16 includes a pair of slave pistons 88a, 88b that receive the rotational driving force of the brake motor 72 and generate the secondary hydraulic pressure.

[0021] The VSA device 18 has a function of assisting in stabilizing the behavior of the vehicle. In detail, as shown in Fig. 1, the VSA device 18 operates the pump motor 79 in response to the behavior of the vehicle, and increases or decreases (adjusts) the secondary hydraulic pressure by driving the pump 135 associated with this operation. By performing these functions, the VSA device 18 has an ABS function that prevents wheel lock during braking by cyclically increasing and decreasing the secondary hydraulic pressure, a TCS (traction control system) function that prevents wheel spin during acceleration, and a function that prevents side slip during cornering.

[0022] The hydraulic braking mechanism 24 has a function of braking each of four wheels (not shown) of the host vehicle. The hydraulic braking mechanism 24 includes calipers 27FR, 27RL, 27RR, and 27FL. When the calipers 27FR, 27RL, 27RR, and 27FL are collectively referred to, they will be abbreviated as "caliper 27." The caliper 27 brakes the four wheels by clamping discs (not shown) provided on each of the four wheels using the primary hydraulic pressure generated by the master cylinder device 14 or the secondary hydraulic pressure generated by the motor cylinder device 16.

[0023] Reference characters Pm, Pp, and Ph denote brake fluid pressure sensors that detect the pressure of the braking fluid (brake fluid) flowing through each of the hydraulic pressure paths 22a to 22f.

[0024] In the vehicle braking device 11 configured as described above, the first and second shut-off valves 60a, 60b are solenoid valves that drive a plunger connected to the valve toward a closed position against the spring force of a return spring (neither shown), similar to the valve shown in Patent Document 1 (see Figure 3 of JP 2012-131438 A).

[0025] The first and second shutoff valves 60a, 60b are provided to be interposed in the hydraulic lines 22a, 22d that communicate between the master cylinder device 14 and the motor cylinder device 16. The first and second shutoff valves 60a, 60b are configured by normally open solenoid valves that operate to open or close the hydraulic lines 22a, 22d.

[0026] In the vehicle braking system 11, when a boost request is generated, the ESB-ECU 29 and the integrated ECU 31 (see FIG. 2; described later in detail) cut off the primary hydraulic pressure generated in the master cylinder device 14 in response to the driver's braking operation using the first and second cut-off valves 60a, 60b. At the same time, a secondary hydraulic pressure corresponding to the amount of braking operation is generated using the brake motor 72 of the motor cylinder device 16.

[0027] In short, in the vehicle braking system 11, the ESB-ECU 29 and the integrated ECU 31, upon receipt of a boost request, shut off (close) the first and second shutoff valves 60a, 60b. Then, with the shut off first and second shutoff valves 60a, 60b as a boundary, a primary hydraulic pressure is generated on the master cylinder device 14 side, which is the upstream side, and a secondary hydraulic pressure is generated on the motor cylinder device 16 side, which is the downstream side.

[0028] The operation of the vehicle brake device 11 when no boost request is generated is as follows. That is, when no boost request is generated, the ESB-ECU 29 and the integrated ECU 31 do not supply power to the first and second cutoff valves 60a, 60b. As a result, the first and second cutoff valves 60a, 60b are opened. Then, in response to the driver's braking operation, the primary hydraulic pressure generated on the upstream side of the master cylinder device 14 is transmitted to the downstream side of the motor cylinder device 16 through the opened first and second cutoff valves 60a, 60b.

[0029] In the ESB-ECU 29 and the integrated ECU 31 in which a boost request has occurred, there are two systems of members having a function of adjusting the secondary hydraulic pressure with the first and second shutoff valves 60a, 60b in a shutoff state. The first system is a first system that adjusts the slide positions of a pair of slave pistons 88a, 88b using the rotational driving force of the brake motor 72 to adjust the secondary hydraulic pressure. The second is a second system that adjusts the secondary hydraulic pressure by driving a pump 135 in accordance with the operation of a pump motor 79. Regarding the adjustment function of the secondary hydraulic pressure, the second system using the pump motor 79 generally has a higher responsiveness than the first system using the brake motor 72.

[0030] [Definitions of terms used in this specification] Here, the terms used in this specification when describing the vehicle braking system 11 will be defined. "Quiet control" refers to control in which, when the plungers (not shown) of the first and second shut-off valves 60a, 60b are driven toward the closed position, the current supplied to the solenoid is gradually increased over time (the slope (rate of change) of the time-varying characteristics is made gentler), thereby suppressing the collision noise generated between the plungers and the case when they reach the closed position.

[0031] There are roughly two types of situations where a "voltage boost request" occurs. The first is a voltage boost request that occurs in response to the driver's braking operation. The second is a voltage boost request that occurs due to control by the integrated ECU 31 based on information related to the driving situation of the vehicle, regardless of the driver's braking operation. Specifically, for example, the integrated ECU 31 outputs the required voltage boost request when a scene occurs in which the vehicle speed of the vehicle exceeds a set value while constant speed travel control related to adaptive cruise control (ACC) is being performed, or when the distance to the preceding vehicle falls below a set value while follow-up travel control related to ACC is being performed.

[0032] The "braking load" in the vehicle braking device 11 is, for example, a brake pad temperature Tpad, which is the temperature of a brake pad provided in a disc brake. The brake pad temperature Tpad is a value detected by the pad temperature sensor 163. However, as the pad temperature Tpad, for example, a value estimated based on parameters such as the vehicle speed and lateral G of the vehicle may be used. The "correlation value of the brake pad temperature" is a concept that encompasses both the detection value of the brake pad temperature Tpad by the pad temperature sensor 163 and the estimated value of the brake pad temperature Tpad.

[0033] The first load threshold Tpadth1 is a threshold used as a reference for determining whether the brake pad temperature Tpad (braking load) has transitioned from the steady state to a warning state requiring caution when the brake pad temperature Tpad (braking load) belongs to a steady state region as shown in FIG. 4 . As shown in FIG. 4, the second load threshold value Tpadth2 is a threshold value serving as a criterion for determining whether or not the brake pad temperature Tpad has transitioned from the warning range to a warning range (the warning range is stricter than the warning range) where a warning to the occupant from the warning range is required when the brake pad temperature Tpad belongs to the warning range. Incidentally, the brake pad temperature Tpad is adopted as an evaluation parameter in the braking performance evaluation system. In the braking performance evaluation system, when the brake pad temperature Tpad exceeds the second load threshold value Tpadth2, it is regarded that the braking load is extremely large, and a determination of poor braking performance related to the vehicle braking device 11 is made. On the other hand, in the vehicle braking device 11 according to the embodiment, when the brake pad temperature Tpad exceeds the first load threshold value Tpadth1 (however, Tpadth1 < Tpadth2), it is regarded that the braking load is large, and the predetermined silent control is prohibited and the non-silent control is executed. As shown in FIG. 4, the third load threshold value Tpadth3 is a threshold value serving as a criterion for determining whether or not the brake pad temperature Tpad has transitioned from the warning range to the steady state range when the brake pad temperature Tpad belongs to the warning range. Note that the third load threshold value Tpadth3, which is a criterion for determining whether or not the brake pad temperature Tpad has transitioned from the warning range to the steady state range, is set to a value smaller than the first load threshold value Tpadth1, which is a criterion for determining whether or not the brake pad temperature Tpad has transitioned from the steady state range to the warning range, for the purpose of avoiding a situation in which a so-called hunting phenomenon occurs in which the brake pad temperature Tpad transitions between the steady state range and the warning range in a short time.

[0034] In the vehicle braking device 11, a case where a boost request occurs in the integrated ECU 31 based on information related to the driving situation of the host vehicle will be described as an example unless otherwise specified.

[0035] 〔Basic operation of the vehicle braking device 11 according to the embodiment〕 Next, the basic operation of the vehicle braking device 11 according to the embodiment will be described. In the vehicle braking device 11, when the motor cylinder device 16 is in a normal state and the ESB-ECU 29 and integrated ECU 31 (see FIG. 2) that perform by-wire control are in a normal state, for example, when the driver performs a braking operation by stepping on the brake pedal 12, the by-wire brake system becomes active.

[0036] In the vehicle braking system 11 under normal conditions, when the driver applies the brakes (however, the same applies when a boost request is generated by the control of the integrated ECU 31 based on information related to the driving conditions of the vehicle, regardless of the driver's braking operation), the first and second shutoff valves 60a, 60b are closed and shut off, while the third shutoff valve 62 is opened. The primary hydraulic pressure generated in the master cylinder 34 is released from the master cylinder 34 to the stroke simulator 64. As a result, even if the first and second shutoff valves 60a, 60b are closed and shut off, a buffer is generated in the primary hydraulic pressure, and the stroke of the brake pedal 12 in accordance with the driver's braking operation is generated.

[0037] In the vehicle braking system 11 under normal conditions, with communication between the master cylinder device 14 and the motor cylinder device 16 being blocked by closing the first and second shut-off valves 60a, 60b, secondary hydraulic pressure is generated in the motor cylinder device 16 in accordance with the driver's braking operation, and the secondary hydraulic pressure thus generated is used to operate the hydraulic braking mechanism 24.

[0038] On the other hand, in the vehicle braking device 11, when the driver applies the brakes in an abnormal state in which the motor cylinder device 16, the ESB-ECU 29, and the integrated ECU 31 do not operate normally, the existing hydraulic brake system becomes active.

[0039] In the vehicle braking system 11 under an abnormal condition, when the driver applies the brakes, the first and second cutoff valves 60a, 60b are opened and the third cutoff valve 62 is closed. The primary hydraulic pressure generated in the master cylinder 34 is transmitted to the hydraulic braking mechanism 24 via the required hydraulic pressure paths 22a to 22f, and causes the hydraulic braking mechanism 24 to operate.

[0040] [Configuration including the ESB-ECU 29 and the integrated ECU 31] Next, a configuration including the periphery of the ESB (Electrical Servo Brake)-ECU 29 and the integrated ECU 31 provided in the vehicle braking system 11 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing a configuration including the periphery of the ESB-ECU 29 and the integrated ECU 31 provided in the vehicle braking system 11.

[0041] As shown in FIG. 2, the vehicle braking system 11 includes an ESB-ECU 29 and an integrated ECU 31.

[0042] 2, the ESB-ECU 29 and the integrated ECU 31 are connected to each other via a communication medium 33 so that they can communicate information with each other. As the communication medium 33, for example, a Controller Area Network (CAN) built in the vehicle can be suitably used. The CAN is a multiplexed serial communication network used for information communication between in-vehicle devices.

[0043] [ESB-ECU29 Configuration] As shown in FIG. 2, an ignition key switch (hereinafter abbreviated as “IG key switch”) 121, a vehicle speed sensor 123, a brake pedal sensor 125, a Hall sensor 127, and brake fluid pressure sensors Pm, Pp, and Ph are connected to the ESB-ECU 29 as input systems.

[0044] The IG key switch 121 is a switch that is operated when supplying a power supply voltage to each of the electrical components mounted on the vehicle via an on-board battery (not shown). When the IG key switch 121 is turned on, the power supply voltage is supplied to the ESB-ECU 29, and the ESB-ECU 29 is started.

[0045] The vehicle speed sensor 123 has a function of detecting the speed of the host vehicle. Information related to the vehicle speed detected by the vehicle speed sensor 123 is sent to the ESB-ECU 29.

[0046] The brake pedal sensor 125 has a function of detecting the amount of operation (stroke amount) and load (pressure) of the brake pedal 12 by the driver. Information related to the amount of operation and load of the brake pedal 12 detected by the brake pedal sensor 125 is sent to the ESB-ECU 29. However, the brake pedal sensor 125 may be a brake switch simply having a function of detecting ON (depressed) / OFF (not depressed).

[0047] The Hall sensor 127 has a function of detecting a rotation angle (current position information in the axial direction of the pair of slave pistons 88a, 88b) of the brake motor 72. Information related to the rotation angle of the brake motor 72 detected by the Hall sensor 127 is sent to the ESB-ECU 29.

[0048] The brake fluid pressure sensors Pm, Pp, Ph have the function of detecting the fluid pressure upstream of the first shutoff valve 60a in the brake fluid pressure system, the fluid pressure downstream of the second shutoff valve 60b, and the fluid pressure within the VSA device 18, respectively. Fluid pressure information of each part in the brake fluid pressure system detected by the brake fluid pressure sensors Pm, Pp is sent to the ESB-ECU 29. Fluid pressure information detected by the brake fluid pressure sensor Ph is sent to the integrated ECU 31 via the ESB-ECU 29 and the communication medium 33.

[0049] On the other hand, as shown in FIG. 2, a brake motor 72 and the first to third shutoff valves 60a, 60b, 62 are connected to the ESB-ECU 29 as an output system.

[0050] As shown in FIG. 2, the ESB-ECU 29 includes a first information acquisition unit 71, a target braking force calculation unit 73, a determination unit 75, and a braking control unit 77.

[0051] The first information acquisition unit 71 has the function of acquiring information relating to the on / off operation of the IG key switch 121, information relating to the vehicle speed detected by the vehicle speed sensor 123, braking operation information relating to the braking operation amount and load detected by the brake pedal sensor 125, rotation angle information relating to the brake motor 72 detected by the Hall sensor 127, and information relating to the brake fluid pressure of each part detected by the brake fluid pressure sensors Pm, Pp, Ph, etc.

[0052] The target braking force calculation unit 73 has a function of calculating a target braking force (target braking torque) according to a required braking amount based on the braking operation amount of the brake pedal 12 by the driver. The target braking force calculation unit 73 also has a function of calculating a target braking force according to a boost request (which occurs regardless of the braking operation of the brake pedal 12 by the driver) sent from the integrated ECU 31 via the communication medium 33.

[0053] The determining unit 75 has a function of determining whether or not the braking load when a boost request occurs is in the steady region. In principle, the determination unit 75 determines that the braking load is in the steady region when the brake pad temperature Tpad (braking load) at the time when a boost request is generated is equal to or lower than a first load threshold Tpadth1 (see FIG. 4). Furthermore, when the brake pad temperature Tpad (braking load) at the time when the boost request is generated exceeds the first load threshold Tpadth1 (see FIG. 4), the determination unit 75 determines that the braking load is in the warning region exceeding the steady region. When the brake pad temperature Tpad (braking load) belongs to the steady region, if the brake pad temperature Tpad exceeds the first load threshold Tpadth1, the ESB-ECU 29 determines that the brake pad temperature Tpad has transitioned from the steady region to the warning region.

[0054] Furthermore, when the brake pad temperature Tpad is in the warning range, the determination unit 75 determines whether the brake pad temperature Tpad exceeds the second load threshold Tpadth2 (see FIG. 4) when the boost request is generated. When the brake pad temperature Tpad is in the warning range and exceeds the second load threshold Tpadth2, the ESB-ECU 29 determines that the brake pad temperature Tpad (braking load) has transitioned from the warning range to the warning range.

[0055] Furthermore, when the brake pad temperature Tpad (braking load) is in the warning range, the determination unit 75 determines whether the brake pad temperature Tpad at the time when the boost request is generated is less than the third load threshold Tpadth3 (see FIG. 4). When the brake pad temperature Tpad is in the warning range and becomes less than the third load threshold Tpadth3 (see time t13 in FIG. 4), the ESB-ECU 29 exceptionally determines that the brake pad temperature Tpad has transitioned from the warning range to the steady range.

[0056] The braking control unit 77 basically has the function of performing braking control to adjust the magnitude of the hydraulic braking force acting in the hydraulic braking mechanism 24 so that it follows a target braking force based on the driver's braking operation.

[0057] If the brake pad temperature Tpad when a boost request is made does not exceed the first load threshold Tpadth1, i.e., if the braking load when a required boost request is made is in the steady state, the braking control unit 77 determines that there is a low probability that the braking performance evaluation system will erroneously evaluate the braking performance as poor, and executes noise reduction control using the second valve closing transient characteristic for the first and second shut-off valves 60a, 60b, starting from the time when the boost request is made (see time t1 in Figure 4).

[0058] On the other hand, if the brake pad temperature Tpad at the time when the pressure increase request is made exceeds the first load threshold value Tpadth1, that is, if the braking load at the time when the first pressure increase request is made is within the warning range, the braking control unit 77 determines that there is a high probability that the braking performance evaluation system will erroneously evaluate the braking performance as poor, and executes non-silence control using the first valve closing transient characteristic for the first and second shut-off valves 60a, 60b, starting from the time when the first pressure increase request is made (see times t7 and t12 in Figure 4).

[0059] The ESB-ECU 29 is configured by a microcomputer equipped with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. This microcomputer reads and executes programs and data stored in the ROM, and operates to perform execution control related to various functions of the ESB-ECU 29, including a function of acquiring various information, a function of calculating a target braking force, a function of determining whether the braking load related to the vehicle braking device 11 is high or low when a required boost request occurs, and a function of performing braking control to adjust the magnitude of the hydraulic braking force.

[0060] [Configuration of Integrated ECU31] As shown in FIG. 2, a radar 151, a camera 153, a wheel speed sensor 155, an accelerator pedal sensor 157, a yaw rate sensor 159, a G sensor 161, and a pad temperature sensor 163 are connected to the integrated ECU 31 as input systems.

[0061] For example, a laser radar, a microwave radar, a millimeter wave radar, an ultrasonic radar, etc. can be appropriately used as the radar 151. The radar 151 is provided behind the front grill of the host vehicle, etc. Target distribution information around the host vehicle obtained by the radar 151 is sent to the integrated ECU 31.

[0062] The camera 153 has an optical axis inclined obliquely downward in front of the vehicle and has a function of capturing an image in the traveling direction of the vehicle. For example, a CMOS (Complementary Metal Oxide Semiconductor) camera or a CCD (Charge Coupled Device) camera can be appropriately used as the camera 153. The camera 153 is provided at the upper center of the windshield of the vehicle. Image information in the traveling direction of the vehicle captured by the camera 153 is sent to the integrated ECU 31 as an image signal generated by an interlace method such as NTSC (National Television Standards Committee).

[0063] The wheel speed sensor 155 has a function of detecting the rotation speed (wheel speed) of each wheel provided on the vehicle. Wheel speed information for each wheel detected by the wheel speed sensor 155 is sent to the integrated ECU 31.

[0064] The accelerator pedal sensor 157 has a function of detecting the amount of accelerator pedal operation (stroke amount) performed by the driver. Accelerator pedal operation amount information detected by the accelerator pedal sensor 157 is sent to the integrated ECU 31.

[0065] The yaw rate sensor 159 has a function of detecting a yaw rate occurring in the host vehicle. Yaw rate information detected by the yaw rate sensor 159 is sent to the integrated ECU 31.

[0066] The G sensor 161 has a function of detecting longitudinal G (longitudinal acceleration) and lateral G (lateral acceleration) occurring in the host vehicle. The G information detected by the G sensor 161 is sent to the integrated ECU 31.

[0067] The pad temperature sensor 163 is provided adjacent to the brake pads (not shown) and has a function of detecting the brake pad temperature Tpad generated by friction braking. The brake pad temperature Tpad is correlated with the braking state of the host vehicle. Therefore, in the present invention, the brake pad temperature Tpad is used as an index for determining the braking performance of the host vehicle. Information on the brake pad temperature Tpad detected by the pad temperature sensor 163 (braking performance information) is sent to the integrated ECU 31.

[0068] As shown in FIG. 2, an alarm device 76 and a pump motor 79 are connected to the integrated ECU 31 as output systems.

[0069] The warning device 76 has a function of issuing a warning by stimulating the driver's hearing, vision, touch, etc., when the braking load of the vehicle is high enough to belong to a warning range (Tpad>Tpadth2), for example.

[0070] For example, when ABS control is required, the pump motor 79 is rotationally driven based on a braking control signal generated in the integrated ECU 31. The pump motor 79 is capable of mainly adjusting the increase / decrease of the secondary hydraulic pressure by driving a pump 135 (see FIG. 1) in accordance with the rotational driving of the pump motor 79.

[0071] Next, the internal configuration of the integrated ECU 31 will be described. The second information acquisition unit 171 has a function of acquiring various types of information including target distribution information detected by the radar 151, travel direction image information captured by the camera 153, wheel speed information detected by the wheel speed sensor 155, accelerator pedal acceleration / deceleration operation amount information detected by the accelerator pedal sensor 157, yaw rate information detected by the yaw rate sensor 159, G information detected by the G sensor 161, and brake pad temperature Tpad detected by the pad temperature sensor 163. In addition, the second information acquisition unit 171 has a function of acquiring vehicle speed information from the vehicle speed sensor 123, which is sent from the ESB-ECU 29 via the communication medium 33, and information related to the amount of operation and load of the brake pedal 12 detected by the brake pedal sensor 125.

[0072] The calculation unit 173 has a function of calculating a slip ratio (slip information) for each wheel based on the vehicle speed information and the wheel speed information for each wheel acquired by the second information acquisition unit 171. The slip information for each wheel calculated by the calculation unit 173 is appropriately referred to in the general control unit 175 when determining whether or not to operate the ABS control.

[0073] The general control unit 175 basically judges whether or not ABS control should be operated based on slip ratio information for each wheel obtained by the calculation unit 173. If the result of this judgment indicates that ABS control should be operated, the general control unit 175 performs braking control to periodically increase and decrease the braking force for each wheel by utilizing the brake fluid pressure adjustment function of the VSA device 18 so as to suppress slip of each wheel.

[0074] In addition, the integrated control unit 175 performs adaptive cruise control (ACC), which includes constant speed control for driving the vehicle at a constant speed based on a preset vehicle speed, and following control for driving the vehicle at a set distance from a preceding vehicle traveling ahead in the direction of travel in the vehicle's travel lane, based on various information including target distribution information detected by the radar 151, travel direction image information captured by the camera 153, and vehicle speed information from the vehicle speed sensor 123. In other words, the integrated control unit 175 performs adaptive cruise control (ACC) of the host vehicle, including acceleration control and deceleration control, without requiring the driver to operate the accelerator pedal or brake pedal, while maintaining the host vehicle's speed within a target vehicle speed range and keeping the vehicle distance from the preceding vehicle at a set distance.

[0075] The integrated ECU 31 is configured by a microcomputer equipped with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. This microcomputer reads and executes programs and data stored in the ROM, and operates to perform execution control related to various functions of the integrated ECU 31, including a function for acquiring various information, a function for calculating slip information for each wheel, an ABS control function, and an adaptive cruise control (ACC) function.

[0076] [Outline of Operation of Vehicle Brake Device 11] Next, the general operation of the vehicle braking device 11 will be described with reference to Fig. 3. Fig. 3 is a flow chart illustrating the operation of the vehicle braking device 11. However, it is assumed that the IG key switch 121 is always on, and the brake pad temperature Tpad is a value that belongs to the steady state region.

[0077] In step S11 shown in FIG. 3, the second information acquisition unit 171 of the integrated ECU 31 acquires various types of information including target distribution information detected by the radar 151, travel direction image information captured by the camera 153, wheel speed information detected by the wheel speed sensor 155, accelerator pedal acceleration / deceleration operation amount information detected by the accelerator pedal sensor 157, yaw rate information detected by the yaw rate sensor 159, G information detected by the G sensor 161, and brake pad temperature Tpad detected by the pad temperature sensor 163.

[0078] In step S12, the integrated ECU 31 checks whether or not a boost request based on the adaptive cruise control (ACC) has occurred. If it is determined that a boost request has not occurred (No in step S12), the integrated ECU 31 returns the process to step S11. On the other hand, if it is determined that a voltage increase request has been made (Yes in step S12), the integrated ECU 31 sends information to the ESB-ECU 29 that a voltage increase request has been made and information on the brake pad temperature Tpad, and causes the process to proceed to the next step S13.

[0079] In step S13, the determination unit 75 of the ESB-ECU 29 determines whether or not the brake pad temperature Tpad at the time when the boost request is generated exceeds the first load threshold value Tpadth1 (see FIG. 4).

[0080] If the result of the judgment in step S13 is that the brake pad temperature Tpad at the time when the voltage increase request occurred does not exceed the first load threshold value Tpadth1 (the braking load at the time when the voltage increase request occurred belongs to the steady region) (No in step S13), the ESB-ECU29 determines that there is a low probability of the braking performance evaluation system making an erroneous evaluation of poor braking performance, and proceeds to the next step S14.

[0081] On the other hand, if the result of the judgment in step S13 is that the brake pad temperature Tpad at the time when the voltage increase request occurred exceeds the first load threshold Tpadth1 (the braking load at the time when the voltage increase request occurred belongs to the warning range) (No in step S13), the ESB-ECU29 determines that there is a high probability that the braking performance evaluation system will erroneously evaluate poor braking performance, and proceeds to the next step S15.

[0082] In step S14, when the braking load when the boost request is generated is in the steady region, the braking control section 77 of the ESB-ECU 29 executes noise reduction control using the second valve closing transient characteristic for the first and second shutoff valves 60a, 60b, starting from the time point when the boost request is generated (see time t1 in FIG. 4). A specific example of the noise reduction control will be described in detail later.

[0083] In step S15, if the braking load when the boost request is generated is within the warning range, the braking control section 77 of the ESB-ECU 29 executes non-silence control using the first valve closing transient characteristic for the first and second shutoff valves 60a, 60b, starting from the time point when the first boost request is generated (see times t7 and t12 in FIG. 4). A specific example of non-silence control will be described in detail later.

[0084] When the processing of step S14 or S15 ends, the ESB-ECU 29 and the integrated ECU 31 end a series of processing flows related to the braking control when the boost request occurs.

[0085] 〔Detailed operation of the vehicle braking device 11〕 Next, the detailed operation of the vehicle braking device 11 will be described with reference to FIG. 4. FIG. 4 is a time chart for explaining the operation of the vehicle braking device 11. FIG. 4(a) shows the change over time of the boost request occurrence situation. FIG. 4(b) shows the change over time of the brake pad temperature Tpad. FIG. 4(c) shows the change over time of the braking load determination result. FIG. 4(d) shows the time characteristics (closing valve transient characteristics) of the solenoid valve drive output related to the first and second shut-off valves 60a, 60b.

[0086] At time t1 in FIG. 4, a boost request occurred based on the adaptive cruise control (ACC). During the period from time t1 to t5, the boost request occurred (see FIG. 4(a)). At the same time t1, the brake pad temperature Tpad belonged to the steady state region (Tpad < Tpadth1). At the same time t1, the braking load determination result was a small load. Therefore, for the boost request that occurred at time t1, the ESB-ECU 29 executed silent control using the second closing valve transient characteristics related to the first and second shut-off valves 60a, 60b starting from the occurrence time (time t1) of the boost request during the period from time t1 to t5.

[0087] The solenoid valve drive output (predetermined second closing valve transient characteristics) shown in FIG. 4(d) sharply rose from 0 (output value for opening the solenoid valve) to the first output value P1 (output value for guiding the solenoid valve to the closing preparation state) at time t1, and then gradually and linearly rose from the first output value P1 to the second output value P2 (output value for guiding the solenoid valve to the closed completion state) during the period from time t1 to t3. The period from time t1 to t3 is a characteristic part of the second closing valve transient characteristics related to the silent control. Thereby, the operating sound (noise) associated with the closing of the first and second shut-off valves 60a, 60b is suppressed as much as possible. During a predetermined period from time t3 to t4, the third output value P3 (a predetermined output value for maintaining the solenoid valve in a completely closed state) is maintained. During an arbitrary period from time t4 to t5 (a remaining period obtained by subtracting the predetermined period from time t1 to t4 from the period from time t1 to t5 during which the required boost request is generated), a predetermined output value capable of maintaining the solenoid valve in a completely closed state is maintained. When the required boost request disappears at time t5, the solenoid valve drive output sharply drops from the first output value P1 to 0.

[0088] At time t7 in FIG. 4, a boost request based on the ACC occurs. The boost request occurs during the period from time t7 to t11 (see FIG. 4(a)). At the same time t7, the brake pad temperature Tpad is in the warning range (Tpad > Tpadth1). At the same time t7, the braking load determination result is a high load. Therefore, in response to the boost request that occurs at the same time t7, the ESB-ECU 29 executes non-silence control using the first valve closing transient characteristic for the first and second shutoff valves 60a, 60b during the period from time t7 to t11, starting from the time point at which the boost request occurs (time t7).

[0089] The solenoid valve drive output (non-default first closing valve transient characteristic) shown in FIG. 4(d) rises sharply from 0 (output value that opens the solenoid valve) to the first output value P1 (output value that leads the solenoid valve to a closing preparation state) at the same time t7, and then rises steeply and linearly from the first output value P1 to the second output value P2 (output value that leads the solenoid valve to a closing completion state) during the period from time t7 to t8. The period from time t7 to t8 is a characteristic portion of the first closing valve transient characteristic related to non-silence control. In particular, the period from time t7 to t8 is set to a shorter time length than the period from time t1 to t3. This makes it possible to suppress as much as possible the erroneous evaluation of poor braking performance by the braking performance evaluation system, even when the braking performance evaluation system is adopted. During a predetermined period from time t8 to t10, the third output value P3 (a predetermined output value for maintaining the solenoid valve in a completely closed state) is maintained. During an arbitrary period from time t10 to t11 (a remaining period obtained by subtracting the predetermined period from time t7 to t10 from the period from time t7 to t11 during which the required boost request is generated), a predetermined output value capable of maintaining the solenoid valve in a completely closed state is maintained. When the required boost request disappears at time t11, the solenoid valve drive output sharply drops from the first output value P1 to 0.

[0090] At time t12 in FIG. 4, a boost request based on the ACC is generated. The boost request is generated during the period from time t12 to t16 (see FIG. 4(a)). At the same time t12, the brake pad temperature Tpad is in the warning region (Tpad > Tpadth3). At the same time t12, the braking load determination result is a high load. Therefore, in response to the boost request generated at the same time t12, the ESB-ECU 29 executes non-silence control using the first valve closing transient characteristic for the first and second shutoff valves 60a, 60b from the time point when the boost request was generated (time t12) as a starting point during the period from time t12 to t16.

[0091] The solenoid valve drive output (non-default first closing valve transient characteristic) shown in FIG. 4(d) rises sharply from 0 (output value that opens the solenoid valve) to the first output value P1 (output value that leads the solenoid valve to a closing preparation state) at the same time t12, and then rises steeply and linearly from the first output value P1 to the second output value P2 (output value that leads the solenoid valve to a closing completion state) during the period from time t12 to t14. The period from time t12 to t14 is a characteristic portion of the first closing valve transient characteristic related to non-silence control. In particular, the period from time t12 to t14 is set to a shorter time length than the period from time t1 to t3. As a result, as with the period from time t7 to t11, even when the braking performance evaluation system is adopted, the erroneous evaluation of poor braking performance by the braking performance evaluation system is suppressed as much as possible. During a predetermined period from time t14 to t15, the third output value P3 (a predetermined output value for maintaining the solenoid valve in a completely closed state) is maintained. During an arbitrary period from time t15 to t16 (a remaining period obtained by subtracting a predetermined period from time t12 to t15 from the period from time t12 to t16 during which the required boost request is generated), a predetermined output value capable of maintaining the solenoid valve in a completely closed state is maintained. When the required boost request disappears at time t16, the solenoid valve drive output sharply drops from the first output value P1 to 0.

[0092] At time t2 shown in Fig. 4, the brake pad temperature Tpad, which had been in the steady region, exceeds the first load threshold Tpadth1. As a result, at the same time t2, the braking load transitions from the steady region to the warning region.

[0093] At time t13 shown in Fig. 4, the brake pad temperature Tpad, which had been in the warning region, becomes less than the third load threshold Tpadth3. As a result, at the same time t13, the braking load transitions from the warning region to the normal region.

[0094] At time t6 shown in Fig. 4, the brake pad temperature Tpad, which had been in the warning range, exceeds the second load threshold value Tpadth2. As a result, at the same time t6, the braking load transitions from the warning range to the warning range. When the braking load (brake pad temperature Tpad) is in the warning range, the braking performance evaluation system regards the braking load as being extremely high and determines that the braking performance of the vehicle braking device 11 is poor. As a result, a warning of poor braking performance is issued to the occupants.

[0095] [Functions and Effects of Vehicle Brake Device 11] Next, the operation and effect of the vehicle braking device 11 will be described with reference to FIG. FIG. 5 is an explanatory diagram showing in comparison the operation of a vehicle braking device according to a comparative example of the present invention and the operation of the vehicle braking device 11 according to the embodiment of the present invention.

[0096] A vehicle braking device 11 based on a first aspect (corresponding to claim 1) is provided with a master cylinder device 14 that generates a primary hydraulic pressure in accordance with a braking operation by a driver, a motor cylinder device 16 that generates a secondary hydraulic pressure corresponding to a target braking force by operating a brake motor 72 and a pump motor 79 (electric actuator) in accordance with a required boost request, first and second shut-off valves 60a, 60b (solenoid valves) of the normally open type that are provided to intervene in hydraulic pressure paths 22a, 22d communicating between the master cylinder device 14 and the motor cylinder device 16 and operate to open or close the hydraulic pressure paths, and a braking control unit (control unit) 77 that performs drive control to close the solenoid valves based on the required boost request, and is a vehicle braking device 11 that applies a braking force to the subject vehicle. The system further includes a determination unit 75 that determines whether the brake pad temperature Tpad (braking load) at the time when the boost request is generated is in a steady region or not. When the brake pad temperature Tpad (braking load) at the time when the boost request is generated exceeds a predetermined first load threshold Tpadth1, the determination unit 75 determines that the braking load is in a warning region that exceeds the steady region. When the brake pad temperature Tpad (braking load) at the time when a boost request is generated is within the warning range, the braking control unit 77 executes braking control (non-silent control) using a first valve closing transient characteristic that extends from the time when the boost request is generated to the time when the solenoid valve is closed. The first valve closing transient characteristic is configured to be set steeper than the second valve closing transient characteristic which occurs from the time a boost request is generated to the time the solenoid valve is closed when the braking load when the boost request is generated is in a steady region.

[0097] According to the vehicle braking device 11 based on the first viewpoint, when the brake pad temperature Tpad (braking load) at the time when a boost request occurs falls within the warning range (Tpad > Tpadth1), the braking control unit 77 performs braking control using the first valve closing transient characteristic (for non-silent control) which is set steeper than the second valve closing transient characteristic (for silent control). Therefore, even when the braking performance evaluation system is adopted, erroneous evaluation of poor braking performance by the braking performance evaluation system can be suppressed as much as possible.

[0098] Here, the vehicle brake device 11 employs a braking performance evaluation system that performs braking performance evaluation based on the consistency related to the correlation between the braking operation amount (stroke amount) and the generated braking force (brake fluid pressure). This braking performance evaluation system uses the correlation characteristic between the stroke amount and the brake fluid pressure under the common condition that the braking load is large (Tpad > Tpadth1) when a required boost request occurs, as shown in Figure 5. As examples of such correlation characteristics, the dotted line in Figure 5 shows a standard reference characteristic, the dashed dotted line in Figure 5 shows a comparative example characteristic with silent control, and the solid line in Figure 5 shows an example characteristic with non-silent control, for comparison.

[0099] The comparative example characteristics with noise reduction control reveal the weakness of noise reduction control (a time delay occurs in blocking the hydraulic path, resulting in fluid loss in the secondary hydraulic pressure and a shift of the comparative example characteristics to the right in FIG. 5 compared to the standard characteristics). In this case, if the braking performance evaluation system is used to evaluate braking performance, it will erroneously evaluate braking performance as poor, especially in areas with a large stroke amount (large pressure boost requirement).

[0100] In contrast, in the example characteristics based on non-silence control, the weaknesses of the silence control are eliminated, and therefore the example characteristics are prevented from shifting to the right side of Fig. 5 relative to the standard characteristics. Therefore, even when the braking performance evaluation is performed using the braking performance evaluation system, there is no risk of the braking performance being erroneously evaluated as poor in the portion with a large stroke amount (large boost demand).

[0101] A vehicle braking device 11 based on a second aspect (claim 2) may adopt a configuration similar to that of the vehicle braking device 11 based on the first aspect, in which the boost request is a boost request based on the target braking force generated regardless of the braking operation by the driver. Here, the boost request is not particularly limited, but may be, for example, a boost request based on adaptive cruise control (ACC).

[0102] According to the vehicle braking device 11 based on the second aspect, it is possible to provide a braking control technology based on the premise of a rapid application to so-called autonomous driving.

[0103] In the vehicle braking device 11 based on the third aspect (claim 3), it is the vehicle braking device 11 based on the first or second aspect, and the determination unit 75 further determines whether or not the brake pad temperature Tpad (braking load) when a boost request occurs exceeds a predetermined second load threshold value Tpadth2. The second load threshold value Tpadth2 is set to a higher value than the first load threshold value Tpadth1. When the brake pad temperature Tpad (braking load) when a boost request occurs exceeds the second load threshold value Tpadth2, the determination unit 75 determines that the brake pad temperature Tpad (braking load) belongs to the warning range. Here, as shown in FIG. 4, the second load threshold value Tpadth2 is a threshold value serving as a reference when determining whether or not the brake pad temperature Tpad has transitioned from the warning range to a warning range (the warning range is stricter than the warning range) that requires a warning to the occupant when the brake pad temperature Tpad belongs to the warning range. Incidentally, the brake pad temperature Tpad is adopted as an evaluation parameter in the braking performance evaluation system. In the braking performance evaluation system, when the brake pad temperature Tpad exceeds the second load threshold value Tpadth2, it is determined that the braking performance of the vehicle braking device 11 is poor on the assumption that the braking load is extremely large. On the other hand, in the vehicle braking device 11 according to the embodiment, when the brake pad temperature Tpad exceeds the first load threshold value Tpadth1 (however, Tpadth1 < Tpadth2), it is assumed that the braking load is large, and the predetermined silent control is prohibited and non-silent control is executed.

[0104] According to the vehicle braking device 11 based on the third perspective, if the brake pad temperature Tpad (braking load) at the time when a boost request occurs exceeds the second load threshold Tpadth2 (where Tpad>Tpadth2>Tpadth1), the judgment unit 75 judges that the brake pad temperature Tpad (braking load) belongs to the warning range, so that in addition to the action and effect of the vehicle braking device 11 based on the first or second perspective, it is possible to appropriately evaluate braking performance based on the brake pad temperature Tpad (braking load).

[0105] A vehicle braking device 11 based on a fourth aspect (claim 4) may be the vehicle braking device 11 based on the third aspect, wherein the magnitude evaluation of the braking load when a boost request occurs is performed based on a correlation value of the brake pad temperature Tpad, and the first load threshold Tpadth1 and the second load threshold Tpadth2 are defined by the correlation value of the brake pad temperature Tpad. The correlation value of the brake pad temperature Tpad is a concept that encompasses both the detected value of the brake pad temperature Tpad and the estimated value of the brake pad temperature Tpad.

[0106] According to the vehicle braking device 11 based on the fourth perspective, the magnitude of the braking load when a voltage increase request occurs is evaluated based on the correlation value of the brake pad temperature Tpad, and the first load threshold Tpadth1 and the second load threshold Tpadth2 are defined by the correlation value of the brake pad temperature Tpad. Therefore, in addition to the action and effect of the vehicle braking device 11 based on the first or second perspective, the magnitude of the braking load can be appropriately evaluated based on the comparison result between the correlation value of the brake pad temperature Tpad and the first load threshold Tpadth1 and the second load threshold Tpadth2.

[0107] A vehicle braking device 11 based on a fifth aspect (claim 5) is a vehicle braking device 11 based on any of the first to fourth aspects, wherein the judgment unit 75 further judges whether the brake pad temperature Tpad (braking load) when a voltage increase request occurs when the braking load belongs to the warning range is less than a predetermined third load threshold Tpadth3, and the third load threshold Tpadth3 is set to a lower value compared to the first load threshold Tpadth1, and if the brake pad temperature Tpad (braking load) when a voltage increase request occurs when the braking load belongs to the warning range is less than the third load threshold Tpadth3, the judgment unit 75 judges that the brake pad temperature Tpad (braking load) has transitioned from the warning range to the steady range.

[0108] As shown in FIG. 4, the first load threshold Tpadth1 is a threshold that serves as a reference for determining whether the brake pad temperature Tpad (braking load) has transitioned from the steady region to the warning region when the brake pad temperature Tpad belongs to the steady region. As shown in FIG. 4, the third load threshold Tpadth3 is a threshold that serves as a reference for determining whether the brake pad temperature Tpad has transitioned from the warning region to the steady region when the brake pad temperature Tpad belongs to the warning region. The third load threshold Tpadth3, which is the criterion for determining whether the brake pad temperature Tpad has transitioned from the warning range to the steady range, is set to a smaller value than the first load threshold Tpadth1, which is the criterion for determining whether the brake pad temperature Tpad has transitioned from the steady range to the warning range, in order to avoid a situation in which the brake pad temperature Tpad transitions between the steady range and the warning range in a short period of time, known as hunting.

[0109] According to the vehicle braking device 11 based on the fifth aspect, if the brake pad temperature Tpad (braking load) at the time when a voltage increase request occurs when the braking load belongs to the warning range is less than the third load threshold value Tpadth3, the judgment unit 75 judges that the brake pad temperature Tpad (braking load) has transitioned from the warning range to the steady range. Therefore, in addition to the action and effect of the vehicle braking device 11 based on the first or second aspect, it is possible to prevent the so-called hunting phenomenon, in which the brake pad temperature Tpad transitions between the steady range and the warning range in a short period of time.

[0110] Other embodiments The above-described embodiments are merely examples of the realization of the present invention. Therefore, the technical scope of the present invention should not be interpreted as being limited by these embodiments. The present invention can be embodied in various forms without departing from the spirit or main characteristics of the present invention.

[0111] For example, an example has been described in which the various functions of the vehicle braking system 11 are divided between the ESB-ECU 29 and the integrated ECU 31, but the present invention is not limited to this example. The present invention may employ an embodiment in which the various functions of the vehicle braking system 11 are integrated into one ECU. [Explanation of symbols]

[0112] 11 Vehicle braking system 14 Master cylinder device 16 Motor cylinder device 22a, 22d Piping tube (hydraulic path) 60a, 60b First and second shutoff valves (solenoid valves) 72 Brake motor (electric actuator) 75 Judgment section 77 Braking control section (control section) 79 Pump motor (electric actuator) Tpad Brake pad temperature (braking load) Tpadth1 First load threshold Tpadth2 Second load threshold Tpadth3 Third load threshold

Claims

1. a master cylinder device that generates a primary hydraulic pressure according to a braking operation by a driver; a motor cylinder device that generates a secondary hydraulic pressure corresponding to a target braking force by operating an electric actuator according to a required boost request; a normally open solenoid valve that is provided in a hydraulic passage that communicates between the master cylinder device and the motor cylinder device and that operates to open or close the hydraulic passage; A control unit that performs drive control to close the solenoid valve based on a required boost request, and applies a braking force to a host vehicle, A determination unit is further provided for determining whether or not a braking load when a boost request is generated is within a steady region. the determination unit, when a braking load at the time when a boost request is generated exceeds a predetermined first load threshold, determines that the braking load belongs to a warning region that exceeds the steady region; the control unit, when the braking load at the time when a boost request is generated is within the warning range, executes braking control using a first valve closing transient characteristic that starts from the time when the boost request is generated and ends when the solenoid valve is closed; the first valve-closing transient characteristic is set to be steeper than a second valve-closing transient characteristic which occurs from the time when a boost request is generated until the solenoid valve is closed when the braking load at the time when the boost request is generated is within the steady region, the determination unit further determines whether or not the braking load at the time when a boost request is generated exceeds a predetermined second load threshold, the second load threshold being set to a value higher than the first load threshold; When the braking load at the time when a boost request is generated exceeds the second load threshold, the determination unit determines that the braking load belongs to a warning range that exceeds the warning range. A vehicle braking system comprising:

2. 2. A vehicle brake system according to claim 1, The boost request is a boost request based on the target braking force generated regardless of the braking operation by the driver. A vehicle braking system comprising:

3. A vehicle braking device as described in claim 1, The magnitude of the braking load when a boost request occurs is evaluated based on a correlation value of the brake pad temperature, and the first load threshold and the second load threshold are defined by the correlation value of the brake pad temperature. A vehicle braking system comprising:

4. A vehicle braking device according to any one of claims 1 to 3, the determination unit further determines whether or not the braking load at the time when a boost request is generated in a case where the braking load belongs to the warning range is less than a predetermined third load threshold, the third load threshold being set to a value lower than the first load threshold; When the braking load is in the warning region and a boost request is generated, the braking load is less than the third load threshold value, and the determination unit determines that the braking load has transitioned from the warning region to the steady region. A vehicle braking system comprising:

Images